The present invention also pertains to the field of modern tree harvesting operations that are carried out using a tree harvesting and processing head mounted to the boom of an excavator-like machine. An example of such tree harvesting and processing heads is illustrated in: U.S. Pat. No. 5,785,101 issued to A. J. Wildey on Jul. 28, 1998.
Modern tree harvesting and processing heads have a chainsaw bar mounted to the lower end thereof for cutting a tree from its stump. The harvesting head has a pair of driven rollers to feed the tree against cutting knives encircling the tree trunk, for cutting the branches off the tree trunk. The driven rollers are also used in combination with the chainsaw for cutting the tree trunk into log lengths.
These tree harvesting and processing machines are operated entirely by hydraulic power and controlled by manual valves. These machines are relatively complicated, and a good understanding and coordination of its elements is required to operate them.
A new operator can damage several chainsaw bars before a training period is completed. For example, if the driven rollers are operated when the chainsaw guide bar is deployed, even a slight movement of the head relative to the tree trunk causes the guide bar to bind in its cut and to bend. Similarly, if any movement of the machine itself occurs, backward, forward or a tilt at the same time as the chainsaw guide bar is being deployed, the bar binds in its cut and gets damaged. It is well known, that any slight deformation in a chainsaw bar is unacceptable. When such an incident occurs, the chainsaw bar must be replaced before harvesting operation can be resumed.
In the past, the structures of some chainsaw guide bars have been modified so that minimum irreversible damage would occur during a mishap by the operator. These repairable guide bars are illustrated and described in the following documents:    U.S. Pat. No. 5,052,109 issued to J. L. Vanderzanden et al. on Oct. 1, 1991, and U.S. Pat. No. 5,884,406 issued to A. Leini on Mar. 23, 1999.
Although these guide bars are claimed to be repairable, there is no apparatus in the prior art to effectively and precisely straighten a damaged guide bar. It is believed that this deficiency in the prior art has largely contributed to limit the commercial success of these repairable guide bars.
For these reasons it is believe that there is a market need for a chainsaw guide bar straightener that is convenient to use in repairing damaged guide bars, whether the guide bars are of the repairable type or of the conventional type.